Heating cable with cold outlets

ABSTRACT

A heating cable with cold outlets, intended mainly for use as immersion heaters and like heating elements, having heating resistance wire of relatively great length having its end brazed to non-heating conductors of greater diameter, the heating wire being covered with a glass fiber braid having a thickness such that the element has a constant cross-sectional dimension, this element being subsequently slipped into a sheath of plastic insulating material, and that said elements are assembled end to end in order to produce a cable of indefinite length subsequently covered with a metal braid and eventually, by extrusion, with a sheath of insulating plastic material.

United States Patent Ragault [451 Apr. 18, 1972 54] HEATING CABLE WITH COLD 3,538,482 11/1970 Dugger ..219/549 OUTLETS FOREIGN PATENTS 0R APPLICATIONS [72] lnvenm" :22;Efigflgig 4,420,828 8/1966 Japan ..338/214 [22] Filed: Aug. 20, 1970 Primary Examiner-Velodymyr Y. Mayewsky pp No 65 398 Att0rneyRobert E. Burns and Emmanuel J. Lobato [57] ABSTRACT [52] US. Cl ..219/553, 219/528, 2313952419; A heating cable with cold outlets, intended mainly for use as 51 I Cl 1 Hosb 3/10 immersion heaters and like heating elements, having heating d 552 553 resistance wire of relatively great length having its end brazed 1 0 can 628, 3:;8/66 to non-heating conductors of greater diameter, the heating wire being covered with a glass fiber braid having a thickness 56] References Cited such that the element has a constant cross-sectional dimen- UNITED STATES PATENTS 2,529,914 11/1950 Challener ..338/214 7/1957 Schrotter et a1. ....338/214 3,284,751 11/1966 Barker et a1, ..338/66 3,348,186 10/1967 Rosen ..338/214 sion, this element being subsequently slipped into a sheath of plastic insulating material, and that said elements are assembled end to end in order to produce a cable of indefinite length subsequently covered with a metal braid and eventually, by extrusion, with a sheath of insulating plastic material.

7 Claims, 2 Drawing Figures PATENTEDAPR 18 I972 A wm a imam H HEATING CABLE WITH COLD OUTLETS BACKGROUND OF THE INVENTION The present invention relates to heating cables having cold outlets of the type intended more particularly for immersion heaters or like heating devices.

DESCRIPTION OF THE PRIOR ART It is known to use heating resistances operating by Joule effect in immersion heaters, within a closed tube of glass, quartz, porcelain, etc.; however, these resistances are attended by many inconveniences making their use rather delicate.

SUMMARY OF THE INVENTION The cable according to the present inventionis characterized in that it consists on the one hand of a conductor having a cross-sectional area calculated according to the desired heating effect and on the other hand of conductors having a greater diameter under these conditions it is an easy matter to wind this wire on a suitable support allowing only the nonheating portions to project beyond the liquid level for obtaining an immersion heater or like element capable of heating any desired bath and characterized by the following advantageous features:

I. The cable is perfectly break-proof, whether during the handling or during actual service;

2. The shape and dimensions of the support are completely optional; as a result, less floor space is required in service and the disposition is more rational in the baths, in comparison with conventional or prior art immersion heaters;

3. The electrical supply connections may be remote from the bath and/or the working site;

4. The copper ends are connected to the 220-Volt mains and the metal screen or sheath is connected to the ground terminal; thus, any dangerous current leak is definitely eliminated; another function of the screen means is that it will greater cross-sectional area producing no heating at all, the 20 distribute the heat by dissipating the Same from a point having ends of these conductors being brazed in order to provide a continuous cable structure.

To avoid any difference in diameter between the heating conductor and the non-heating conductors, one or several layers of heat resisting fibers adapted to be braided are disposed around the heating conductor, for example glass fiber braids, to eliminate any difference in diameter between the conductors.

By way of example, the heating cable may comprise a stainless steel resistor-forming section having a diameter of 1 millimeter and brazed at its ends to a copper wire having a diameter of at least 2 mm, the successive cold and hot sections being silver-brazed. A polytetrafluorethylene braid is slipped on this assembly of heating wires and cold wires. Thus, a cable comprising for example a 15.5-meter long heating conductor and two cold conductors, one 0.85-m long and the other 1.65-m long, is obtained.

Heating resistors are brazed to the free ends of this cable, and so forth, until a relatively long cable comprising in succession relatively long heating resistors separated by relatively short cold conductors of unequal lengths, is obtained.

On the cable thus obtained a metal braid is formed by using, for instance l-mm copper wire, and the resulting braid is covered by extrusion with a fluorethylene-propylene.

To obtain immersion heaters, it is only necessary to cut this cable in order to obtain elements or sections comprising about meters of heating resistance with a 0.85-m long cold conductor fonning an outlet at one end and a 1.65-m long cold conductor forming an outlet at the opposite end.

In the example described hereinabove, the resistance is slightly in excess of 3 'Kw under a 220-Volt current, the polytetrafluorethylene charge being for example 300 watts/sq.dm watts/sq.in.) and the fluorethylenepropylene charge 180 watts/sq.dm. (12 watts/sq.in).

According to a modified form of embodiment the abovedescribed steps concerning the preparation of a constant-section cable are firstly adhered to, then these elements are brazed end to end to constitutea cable of indefinite length, and this cable is covered with a glass fiber braid. Then this braid is coated with silicone rubber, or alternatively the surface of the previously heated wire is coated directly with a fluidized polyfluorethylene powder bonded to the hot wires by passing the assembly through an oven, possibly with a step consisting in mechanically crushing and welding the grains to one another. A metal braid is subsequently applied on this insulating sheath and the operation is completed as in the preceding example.

In the above mentioned example, by cutting the cold copper sections across the joints between the sheath sections, which are determined for example by measuring the known lengths of the hot and cold portions, identical electric resistances are obtained which approximate 2.8 Kw under 220 volts, with end plastic sheath for example of sections the length of which corresponds to the conductors of a tendency to overheating to adjacent points; thus, no overheating can take place not only at the points of contact with said support but also at possible crossings and superpositions of heating sections;

5. A universal chemical resistance is achieved, due to the properties of the extruded plastic material constituting the outermost coating; thus, the same therrnoprobe may be used in succession in different media, in contrast to the sheaths of conventional immersion heaters of which the resistance is frequently specific of only one medium;

6. In electrolytic baths the fact that the immersion heater is completely insulated will avoid the known shunt current effect frequently constituting a cause of damage or interference with immersion heaters having conductive sheaths;

7. Also due to the particular properties of the plastic materials constituting the outermost coatings or sheats, and to a lower emission of heat per heating surface unit, possible solid deposits such as those tending to develop in bright nickel-plating baths on the heating devices associated with these baths, will not be formed with the same facility with the device of this invention, and if they develop nevertheless they can be removed very easily by a simply brushing step, in contrast with the hardly removable incrustation observed in conventional installations.

BRIEF DESCRIPTION OF THE DRAWING The heating cable according to this invention will now be described more in detail with reference to FIGS. 1 and 2 of the attached drawing illustrating diagrammatically by way of example axial sections of component elements of this cable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The heating resistance 1 of a diameter of, say, a resistivity of 70 microhms per sq.cm (450 microhms per sq.in.), is brazed at its ends 2 and 3 to cold conductors 4, 5 consisting of non-heating copper wires having a diameter of, say, 2 mm.

Braided on the heating wire 1 is a l-mm thick sheath 6 of insulating material for giving to this cable section the same diameter as the non-heating wires 4 and 5 thereof.

An insulating sheath 7, for example a plastic sheath made of Teflon and having a thickness of 0.2 to 0.5 mm, is slipped on the assembly thus formed, i.e. comprising a heating conductor and two cold conductors. The element thus obtained is extended on either side in order to comprise successive elements including heating conductors each of a length of, say, 15.5 meters, with cold conductors 4, 5 having a length, for each element, of 0.80 m on one side and 1.60 m on the other side. Then a metal braid 8 for example of 0.1 mm copper wire is braided on this continuous cable, and a plastic sheath 9 for example of Teflon is formed by extrusion on this braid.

To obtain immersion heater elements, it is only necessary to cut this infinite cable along the lines X-X in order to produce 1 mm, having elements comprising each a heating conductor 1 and two cold conductors 4 and 5, having a length of 0.80 m on one side and 1.60 m on the other side, for instance. The cold conductors form outlet terminals for the heating element.

In the modified form of embodiment illustrated in FIG. 2 of the drawing the procedure employed is initially the same as in the case of FIG. 1, that is, similar elements are assembly which comprise each a heating conductor 1 brazed at its ends to cold conductors 4, 5 of unequal length, these elements being assembled end-to-end to produce a cable of indefinite length. Then this cable is covered by braiding thereon a glass fiber braid 6 in order to form a constant diameter cable. This braid 6 is then covered with a layer consisting for example of silicone rubber or plastic material such as polytetrafluorethylene, which may be in the form of a fluidized powder remelt on the hot cable.

Braided on this layer 10 is a metal sheath 8 and the latter is covered in turn with a sheath 9 of insulating material, as in the preceding example.

What I claim is:

1. Heating cable with cold outlets, intended mainly for use as electric immersion heaters and like heating elements, comprising alternately a succession of heating resistance wires of relatively great length and of non-heating conductive wires of greater cross-sectional dimension than said resistance wires, the ends of the heating wires being soldered to the ends of the conductive wires, a glass fiber braid formed on and around each of said heating wires and having a thickness such that the cross-sectional dimension of the heating wires with said glass fiber braids is the same as that of said conductive wires, an insulating sheath and a metal braid of uniform diameter surrounding the assembly of the heating wires and conductive wires and a sheath of insulating plastic material extruded over the assembly.

2. Heating cable as set forth in claim 1, wherein said heating resistance wires consist of stainless-steel resistor having a diameter of 0.8 mm, and said conductive wires consist of copper wire having a diameter of 1.6 mm.

3. Heating cable as set forth in claim 1, wherein the plastic sheath covering the assembly of heating wires and conductive wires consists of polytetrafluoroethylene.

4. Heating cable as set forth in claim 1, wherein said metal braid is made from 0. 1 mm copper wire.

5. A section of heating cable for an electric immersion heater as set forth in claim 1, wherein each of said heating resistance wires is 15.5 meters long and two adjoining said conductive wires consist of copper wire having a length of 0.85 meter on one side and 1.65 meters on the other side of said resistance wire.

6. Heating cable as set forth in claim 1, wherein the assembly comprising said braid covered resistance wire and said conductive wires have braided thereon another layer of fiber glass surrounded by said insulating sheath and metal braid.

7. Cable as set forth in claim 6, wherein said glass fiber braid covering the heating and cold conductors is coated in the hot state with a fluidized powder of plastic material of the polytetrafluorethylene type bonded thereon by the application of heat, said layer being subsequently covered with said metal braid and with said insulating external sheath. 

1. Heating cable with cold outlets, intended mainly for use as electric immersion heaters and like heating elements, comprising alternately a succession of heating resistance wires of relatively great length and of non-heating conductive wires of greater cross-sectional dimension than said resistance wires, the ends of the heating wires being soldered to the ends of the conductive wires, a glass fiber braid formed on and around each of said heating wires and having a thickness such that the crosssectional dimension of the heating wires with said glass fiber braids is the same as that of said conductive wires, an insulating sheath and a metal braid of uniform diameter surrounding the assembly of the heating wires and conductive wires and a sheath of insulating plastic material extruded over the assembly.
 2. Heating cable as set forth in claim 1, wherein said heating resistance wires consist of stainless-steel resistor having a diameter of 0.8 mm, and said conductive wires consist of copper wire having a diameter of 1.6 mm.
 3. Heating cable as set forth in claim 1, wherein the plastic sheath covering the assembly of heating wires and conductive wires consists of polytetrafluoroethylene.
 4. Heating cable as set forth in claim 1, wherein said metal braid is made from 0.1 mm copper wire.
 5. A section of heating cable for an electric immersion heater as set forth in claim 1, wherein each of said heating resistance wires is 15.5 meters long and two adjoining said conductive wires consist of copper wire having a length of 0.85 meter on one siDe and 1.65 meters on the other side of said resistance wire.
 6. Heating cable as set forth in claim 1, wherein the assembly comprising said braid covered resistance wire and said conductive wires have braided thereon another layer of fiber glass surrounded by said insulating sheath and metal braid.
 7. Cable as set forth in claim 6, wherein said glass fiber braid covering the heating and cold conductors is coated in the hot state with a fluidized powder of plastic material of the polytetrafluorethylene type bonded thereon by the application of heat, said layer being subsequently covered with said metal braid and with said insulating external sheath. 